This invention relates to tufting machines and more particularly to indexing apparatus for laterally shifting the needle bar or for feeding the backing material in a selectively controlled stepwise manner so as to provide a patterning effect in the tufted fabric produced thereby to extend the patterning capabilities of the tufting machine.
In the production of tufted fabric it is known to jog or shift the needle bar in its longitudinal direction tranversely across the tufting machine relatively to the base material in order to create various pattern effects, to break up the unattractive alignment of the longitudinal rows of tufts and to reduce the affects of streaking which results from variations and colorations of the yarn.
Various devices have been proposed and are in use for controllably applying a step-wise force to the needle bar of the tufting machine in accordance with a pattern. Such needle shifting or stitch placement drives conventionally fall into two categories. The first category is that of the cam driven type whereby a rotating plate cam, driven in timed relationship with the tufting machine mainshaft, is drivingly engaged with the needle bar so as to effect the required displacement thereof. The second category is that of the programmable type which may be hydraulically or pneumatically driven, or driven mechanically through some form of programmable indexing device whereby a ram is drivingly engaged with the needle bar so as to effect the required displacement thereof. Examples of such drives are illustrated in U.S. Pat. Nos. 3,964,408 and 3,972,295, which utilize pawl and ratchet devices, U.S. Pat. No. 4,010,700 which utilizes an indexing device and 4,173,192 which uses a hydraulic actuator. In U.S. Pat. No. 4,392,440, an indexing device is proposed for extending the pattern capabilities of a cam by means of a device which intermittently drives the cam. In U.S. Pat. No. 4,653,413 an epicyclic drive effectively extends the range of the cam systems by driving the cam with an oscillating motion superimposed onto a constant speed input to provide a cyclically variable input to drive the cam, and by varying the amplitude of oscillation, a single cam may provide a multiplicity of patterns.
In U.S. Pat. No. 4,557,208 a backing material feed drive system is proposed including an indexing drive device for driving the feed rollers in a controllably varying manner.
In certain applications it is desirable to, for example, laterally step the needle bar selectively in one, two, or three steps during a particular machine cycle. This is highly desirable when utilizing two sliding needle bars which can be shifted independently so as to provide unique patterning effects. In the prior art devices such patterning effects have been provided either by computer controlled hydraulic actuators or by separate and independent cam drives. Although the cam drive system is exceptionally reliable it has a disadvantage of not being programmable and wherever the pattern is changed, the cams must be changed. The hydraulically actuated drive, and pneumatically actuated drives, are electronically programmable, but the skills in programming the electronics are not readily available in most carpet mills, where such apparatus operates. Accordingly, either a substantial number of cams or electronic chips must be inventoried in the mill, or when a new pattern is required, such cams must be designed and manufactured or such chips must be programmed at locations other than at the mill, thereby necessitating the inherent delays.
Ideally a mechanically programmable drive system which is highly accurate and which can provide a multiplicity of gauge movements to the needle bar is highly desirable. Such a system could overcome the need to inventory cams or electronic chips and be within the capabilities of the tufting machine mill operators to program selectively as required. Although extensive work has been directed in this area, the prior art has not developed such a system.